Fracking perforation guns and depeleted uranium!

What has been uncertain is the strength of the charges used. Compared to conventional reservoirs which only need mild stimulation to trigger flows, the density of shale makes it much harder to ‘punch’ through, and in order to get any flow at all, fractures need to be extensive. The temptation must be to have much stronger charges in shale beds than conventional reservoirs, leading to increased difficulties in control and uncertain outcomes. It appears to be an area of considerable R&D by operators like Schlumberger:https://www.slb.com/~/media/Files/resources/oilfield_review/ors06/aut06/new_practices.pdf

I doubt anyone would be foolish enough to use nitro or plastic explosives when searching for methane! Have heard rumours about DU (Depleted Uranium) being used in drill bits before, but have never seen any evidence.

Copying Andy Chyba, who knows far more about these things than I do and may be able to guide you to some reliable sources.